This invention generally relates to a powdery composition comprising dried viable cell mass of the genus Bifidobacterium (hereinafter described as Bifidobacteria cells) to be orally administered for initiation or conservation of favorable intestinal flora.
More particularly this invention relates to a powdery composition comprising a powder containing viable Bifidobacteria cells and lactulose which composition has a high survival rate for a long period of storage.
It has been well known that Bifidobacterium is normally found in the human intestine, and is one of the useful microorganisms.
Also it has been known that oral administration of viable Bifidobacteria cells is effective for preventing and treating bowel complaints, particularly diarrhea, intestinal catarrh, dyspepsia, constipation and intestinal microbial substitution (microbisme substitute) after treatment with antibiotics. For such purposes, a variety of powdery compositions containing dried viable Bifidobacteria cells have been sold in the market.
In the conventional powdery compositions, however, the survival rate of Bifidobacteria cells has been unsatisfactorily low, and it has been a basic problem to improve the cell survival rate and preserve the viable count of Bifidobacteria cells at a certain level for a long period of storage.
For instance, the content of viable Bifidobacteria cells in 1 gram of the powdery products supplied by the 12 companies in Japan and of the powdered milk containing Bifidobacteria cells and a small portion of lactulose supplied by a certain German company is generally as low as 5 or 6.times.10.sup.7 or so. Moreover, the viable count of the cells in these products rapidly decreases during storage.
Under such circumstances, many attempts at improving the shelf life of products containing Bifidobacteria cells have been made.
Ohta reported in his research note entitled "Research for freezing and freeze drying Lactobacillus bifidus" in the Japanese journal "Ochanomizu Igaku Zasshi (Ochanomizu Medical Journal)" Vol. 7, No. 11 (1959), pp. 2967-2975, concerning the viability of freeze dried Bifidobacteria cells which were prepared with various drying methods and suspending agents.
In this research note, he reported that sodium glutamate as a suspending medium for freeze drying of Bifidobacteria cells may give a better cell survival rate when freeze dried Bifidobacteria cells were stored at 37.degree. C., and skim milk, soluble starch and sucrose followed thereafter. The best results were observed when sodium glutamate in 3% (by weight) concentration was used, but the survival rate in this best case decreased to 1% after only 2 months storage.
Smiha reported in the "Journal of Food Science" Vol. 39 (1974) pp. 641-642 that a 55% survival rate after 2 months storage at 30.degree. C. was obtained when Lactobacillus bifidus (old scientific nomenclature for genus Bifidobacterium) cells were subjected to freeze drying using a suspending agent of skim milk fortified with ascorbic acid, thiourea and ammonium chloride. This value is somewhat higher but the product prepared by this method is not preferable for the usual distributing system, since the viable count of Lactobacillus bifidus in this product is considered to rapidly decrease upon prolonged storage, i.e., more than 2 months.
As mentioned above, decreased survival rate during storage greatly impairs the commercial value of such powdery products, since the density of Bifidobacteria cells decreases during storage even if the products initially have a high cell density.
Consequently, in the conventional products containing viable Bifidobacteria cells, lactose, starch and the like have been added as a suspending medium for protection of the cells. Nevertheless, the conventional powdery compositions containing a known suspending medium do not achieve sufficient viability. Such a suspending medium, therefore, does not actually function to protect the cells, but rather only for diluting the freeze dried Bifidobacteria cells. In fact, the density of viable Bifidobacteria cells in the powdery products presently distributed in the market is very low.
There has not been known a powdery product containing dried Bifidobacteria cells which is capable of retaining a high density of viable cells during a prolonged storage period.
Therefore, it is an object of the present invention to provide a powdery composition containing dried viable Bifidobacteria cells in a high cell density which is capable of a higher cell survival rate during a long period of storage.
It is another object of the invention to provide a powdery composition containing dried viable Bifidobacteria cells which is capable of establishing Bifidobacterium flora in the intestinal tract when it is orally administered.
A further object of this invention is to provide a powdery composition comprising a powder containing viable Bifidobacteria cells and lactulose containing powder.